volatile原子测试（已解决）

Question

做一个实验，期待发生bug，为啥却始终看不到？
场景：有n个红包放在数组中用false表示，有m个线程来抢，抢完设置true
期待错误：判断是false，就执行设置true。期待同时有多个线程判断了false，但只有一个设置成功，最终因为线程不够，数组中仍剩下false
结果：每次运行都是n个true

public class MyVolatile {
        private volatile static boolean[] account; 
        public static void main(String[] args) {
                //1 init
                account = new boolean[50];
               // Arrays.fill(account, false);默认初始化为假

                //2 iterate
                ArrayList<Thread> arrayList = new ArrayList<Thread>();
                for (int i = 0; i < 52; i++) {
                        Thread thread = new Thread(new Runnable() {

                                @Override
                                public void run() {
                                        for (int j = 0; j < account.length; j++) {
                                                if (account[j] == false) {
                                                        account[j] = true;
                                                        System.out.println("yes");
                                                        return;
                                                } 
                                        }
                                        System.out.println("no --- "+Thread.currentThread());
                                }
                        });
                        arrayList.add(thread);
                }
                for (Thread thread : arrayList) {
                        thread.start();
                }

                //3 end
                try {
                        Thread.sleep(5000);
                } catch (InterruptedException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                }
                int total = 0;
                for(int j=0; j<50; j++){
                        total += account[j] ? 1 : 0;
                }
                System.out.println("finally:" + total );
        }

}